Tribrach device

ABSTRACT

An improved tribrach device for attaching an optical sighting instrument to a support such as a tripod. The tribrach device includes a pivotable locking ring for securing the legs of the sighting instrument to the tribrach. The locking ring is biased towards its locked position and is easily unlocked when desired. A laser beam is projected upwardly and downwardly along a vertical axis.

FIELD OF THE INVENTION

This invention relates to tribrach devices. More particularly, thisinvention relates to an improved tribrach device for supporting anoptical sighting device, i.e., for surveying purposes.

BACKGROUND OF THE INVENTION

Optical instruments are used for surveying purposes and are supportedon, and attached to, the upper end of a tripod by means of a tribrachdevice. The tribrach is secured on its underside to the upper end of thetripod, and the optical sighting instrument is detachably secured to thetop of the tribrach device.

With a conventional tribrach device, the three depending legs of anoptical sighting device are received in three openings in the tribrach,after which the legs are locked by rotating a small tab or lever to movea cam against the legs in the openings. One of the three openings in thetribrach is elongated to compensate for any irregularities in centeringthe device in the tribrach. This allows the device being fastened to thetribrach to deviate in position. Such a mechanism for locking the legsin the tribrach device is cumbersome and often fails to provide a securelocking of the legs in the tribrach. Thus, during windy conditions, theoptical instrument can become loosened because the lock mechanism doesnot securely hold the legs of the instrument in the receiving openingsin the tribrach. Also, the lever on the locking mechanism is difficultto operate while wearing gloves (e.g., during cold weather).

Another problem associated with the use of optical sighting instrumentsis that they must be vertically aligned over a control point (e.g., aground mark, stake, monument, etc.). This can be a time-consumingprocedure.

Recently, U.S. Pat. No. 5,159,760 described a device for aligning ageodetic instrument over a defined ground mark using a collimated laserbeam in a manner such that the vertical distance between the definedground mark and the sighting line of the geodetic instrument can bemeasured. Such device does not cure the problems associated with lockingthe geodetic instrument to the tribrach. Also, the device is notsuitable for use in subterranean situations where it is necessary toalign an optical sighting device vertically beneath a marker which islocated above the instrument (e.g., where the marker is located on theceiling of a tunnel).

Yet another problem or disadvantage which is common in conventionaltribrachs is that they are composed of a cast material which is prone totemperature fluctuations and are also easily damaged (even with minorimpacts).

U.S. Pat. No. 3,471,234 describes a laser beam projector for use insurveying operations. Such patent does not describe a tribrach havingthe advantages provided by the present invention.

U.S. Pat. No. 4,309,010 describes a tripod with an adjustable supportsurface for supporting various types of objects(e.g., cameras,projection apparatus, geodetic instruments, antennas, etc.). This patentdoes not describe a tribrach having the advantages provided by thisinvention.

U.S. Pat. No. 4,832,296 describes a giant tripod assembly for supportinglaser beam generators. This patent does not describe a tribrach of thetype provided by this invention.

There has not heretofore been provided a tribrach device having theadvantages provided by the present invention.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided an improvedtribrach device which includes a laser adapted to project a light beamvertically down to a ground point and is also adapted to project a lightbeam vertically upward to a reference marker located above an opticalsighting instrument. Further, the improved tribrach device includeslocking means for easily and securely locking the legs or pins of anoptical sighting instrument to the tribrach device. The locking means isvery easy to operate, even while wearing gloves. Also, the locking meanssecurely locks the legs or pins of the optical sighting instrument tothe tribrach so that the instrument remains very secure even during verywindy conditions. The locking means also aligns the instrument with thetribrach device.

The tribrach is composed of a rigid and durable material. Consequently,it can easily withstand impact without danger of it breaking or beingotherwise damaged.

Other advantages of the tribrach of this invention will be apparent fromthe following detailed description and the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in more detail hereinafter with reference tothe accompanying drawings wherein like reference numbers refer to thesame parts throughout the several figures and wherein:

FIG. 1 is a perspective view of a preferred embodiment of a tribrachdevice of the invention;

FIG. 2 is an explosion cross-section view showing the tribrach device ofFIG. 1;

FIG. 3 is a top view of the tribrach device of FIG. 1;

FIG. 4 is a top view of the locking means used in the tribrach device ofthe invention;

FIG. 5 illustrates use of the tribrach device in an undergroundenvironment; and

FIG. 6 is a side elevational view showing the tribrach device on theupper end of a tripod and supporting an optical sighting instrument.

DETAILED DESCRIPTION OF THE INVENTION

In the drawings there is shown an improve tribrach device 10 of theinvention which comprises upper body member 12A and lower body member12B. Preferably each body member is composed of a very durable and rigidmaterial which is impact-resistant and is able to withstand widetemperature variations without damage. The thickness of each body memberis preferably about one inch.

Preferred material for the tribrach device is tempered aluminum (i.e.,“T” or “P” series aluminum) which is aircraft grade as opposed to castor forged aluminums. It is also possible to use materials such astitanium or other such durable materials. Preferably non-ferrousmaterials are used so as to avoid corrosion.

The upper body member 12A includes three precision machined openings 15to receive the three pins or legs of an optical sighting device. Thediameter of the openings may vary, so long as all of such openings inthe tribrach have the same diameter (e.g., 0.5 inch). The openings areequidistantly spaced.

A leveling bubble 18 is positioned in a recess in the upper surface ofthe body member 12A. The leveling bubble is secured in the recess and isnot movable. It is press-fitted into the recess.

The locking means in the tribrach comprises a ring 14 having threeoutwardly-projecting locking lugs 14B equidistantly spaced at theperiphery of the ring. Each locking lug includes an outer edge which isreferred to herein as a spiral curve which serves to center the pins orlegs of the sighting device relative to the tribrach device.

A downwardly-projecting pin 17 near the periphery of the ring 14 isreceived in a opening 19A in member 19 which is sandwiched between upperand lower body members 12A and 12B. A coil spring 21 biases the ring ina manner such that the ring rotates in a horizontal plane (in thedirection shown by the arrow) to a normally-locked position.

Preferably there are at least two levers or handles 14A projectingoutwardly from the periphery of the ring to enable a workman to easilyrotate or pivot the ring when desired in order to move the ring to itsunlocked position, i.e., where the lugs 14B enable the legs of theoptical sighting instrument to be inserted or removed from the openings15 in body member 12A.

The pivot point of the locking ring is the vertical pin 17 as describedabove. For example, the pin 17 may be secured to the underside of thelocking ring and may be received in a recessed opening in member 19. Thespring 21 urges the locking ring toward its normal locked position suchthat the lugs on the ring are urged against the legs of the sightingdevice supported on the tribrach. Thus, the legs are always locked inposition until the workman grasps one of the handles or levers andpivots the locking ring in a direction against the force of the spring.

The tribrach device includes a laser generator 20 such as a 670 nm diodelaser which is secured in a recess or cavity in member 19. A prism 22 isalso secured in member 19 directly in line with the centerline of thelaser beam generator so that the laser beam is reflected from ahorizontal plane to a vertical plane. This provides a laser beam whichprojects vertically upward and downward. Thus, the laser beam can beused to align the optical sighting instrument vertically over a groundmarker or under a ceiling marker (e.g., in a tunnel or mine). The laseris battery powered and is activated by means of switch 16.

The lower body member 12B is attached to the upper body member 12a bymeans of three threaded bolts 23 each of which passes through an opening12C in member 12B and is threadably received in opening 12D in bodymember 12A. The lower end 23A of bolt 23 is ball-shaped and fits intothe complimentarily-shaped recess 12E. Set screw 28 holds bolt 23 in theupper end of recess 12E. Nut 24 is secured to bolt 23 by set screw 27.By rotating nut 24 on one or more of bolts 23, the attitude of bodymember 12A relative to body member 12B may be adjusted (e.g., to levelbody member 12A). Body member 12a includes a central opening 25 and bodymember 12B includes central opening 26 to enable the laser beam to bedirected upwardly and downwardly through the tribrach device.

The tribrach device can be used in a variety of situations, even duringdeteriorating weather conditions and depleted light. The tribrach canalso be used in subsurface applications such as aqueducts, mines,caverns, tunnels and large underground utility lines. These applicationsutilize monuments and points of reference in the ceiling of thesubsurface throughway. FIG. 5 illustrates use of the tribrach device ona tripod 40 in an underground environment. Any conventional instrumentmay be positioned on and attached to the tribrach device. FIG. 6illustrates the use of the tribrach device on a tripod 40 for supportinga conventional optical sighting instrument 30.

Other variants are possible without departing from the scope of thisinvention.

What is claimed is:
 1. A tribrach device comprising: (a) an upper bodymember including a plurality of apertures extending verticallytherethrough; and wherein said upper body member also includes a lightbeam opening extending vertically therethrough; (b) a lower body memberattached to said upper body member; wherein said lower body memberincludes a light beam opening extending vertically therethrough; (c) alocking ring disposed between said upper and lower body members; whereinsaid locking ring includes a plurality of outwardly-extending lugscorresponding to the number and position of said apertures; wherein saidlocking ring is pivotable in a manner such that said lugs move between alocking position and a retracted position; wherein when said lockingring moves toward said retracted position said lugs move away from saidapertures, and when said locking ring moves toward said locking positionsaid lugs move toward said apertures; and further including biasingmeans for biasing said locking ring toward said locking position; and(d) a laser beam generator between said upper and lower body members forgenerating a visible light beam; and further including means fordirecting said light beam upwardly and downwardly along a vertical axisthrough said light beam openings in said upper body member and saidlower body member.
 2. A device in accordance with claim 1, wherein saidmeans for directing said light beam upwardly and downwardly along saidvertical axis comprises a prism which intersects said visible light beamfrom said generator.
 3. A device in accordance with claim 1, furthercomprising a leveling bubble secured in said upper body member.
 4. Adevice in accordance with claim 1, wherein there are three saidapertures and three said lugs.
 5. A device in accordance with claim 1,wherein said lugs are disposed beneath said apertures.
 6. A device inaccordance with claim 1, wherein said locking ring includes a pluralityof outwardly-projecting handles.
 7. A combination comprising: (a) anoptical sighting instrument having downwardly extending legs; (b) atribrach device comprising: (i) an upper body member including aplurality of apertures extending vertically therethrough; and whereinsaid upper body member also includes a light beam opening extendingvertically therethrough; (ii) a lower body member attached to said upperbody member; wherein said lower body member includes a light beamopening extending vertically therethrough; (iii) a locking ring disposedbetween said upper and lower body members; wherein said locking ringincludes a plurality of outwardly-extending lugs corresponding to thenumber and position of said apertures; wherein said locking ring ispivotable in a manner such that said lugs move between a lockingposition and a retracted position; wherein when said locking ring movestoward said retracted position said lugs move away from said apertures,and when said locking ring moves toward said locking position said lugsmove toward said apertures and further including biasing means forbiasing said locking ring toward said locking position; and (iv) a laserbeam generator between said upper and lower body members for generatinga visible light beam; and further including means for directing saidlight beam upwardly and downwardly along a vertical axis through saidlight beam openings in said upper body member and said lower bodymember; wherein said legs of said instrument are received in saidapertures and are secured by said lugs on said locking ring.
 8. Atribrach device comprising: (a) an upper body member including aplurality of apertures extending vertically therethrough; and whereinsaid upper body member also includes a light beam opening extendingvertically therethrough; (b) a lower body member attached to said upperbody member; wherein said lower body member includes a light beamopening extending vertically therethrough; (c) a locking ring disposedbetween said upper and lower body members; wherein said locking ringincludes a plurality of outwardly-extending lugs corresponding to thenumber and position of said apertures; wherein said locking ring ispivotable in a manner such that said lugs move between a lockingposition and a retracted position; wherein when said locking ring movestoward said retracted position said lugs move away from said apertures,and when said locking ring moves toward said locking position said lugsmove toward said apertures; and further including biasing means forbiasing said locking ring toward said locking position.
 9. A device inaccordance with claim 8, further comprising a leveling bubble secured insaid upper body member.
 10. A device in accordance with claim 8, whereinthere are three said apertures and three said lugs.
 11. A device inaccordance with claim 8, wherein said lugs are disposed beneath saidapertures.
 12. A device in accordance with claim 8, wherein said lockingring further includes at least one handle projecting outwardlytherefrom.
 13. A device in accordance with claim 8, wherein said bodymembers are composed of tempered aluminum.
 14. A tribrach devicecomprising: (a) an upper body member including a light beam openingextending vertically therethrough; (b) a lower body member attached tosaid upper body member; wherein said lower body member includes a lightbeam opening extending vertically therethrough; (c) a laser beamgenerator between said upper and lower body members for generating avisible light beam; and further including means for directing said lightbeam upwardly and downwardly along a vertical axis through said lightbeam openings in said upper and lower body members.
 15. A device inaccordance with claim 14, wherein said means for directing said lightbeam upwardly and downwardly along said vertical axis comprises a prismwhich intersects said visible light beam from said generator.
 16. Adevice in accordance with claim 14, further comprising a leveling bubblesecured in said upper body member.
 17. A device in accordance with claim14, wherein said body members are composed of tempered aluminum.
 18. Atribrach device comprising: (a) an upper body member including a lightbeam opening extending vertically therethrough; (b) a lower body memberattached to said upper body member; wherein said lower body memberincludes a light beam opening and a plurality of bolt openings extendingvertically therethrough; wherein said lower body member is attached tosaid upper body member by means of a plurality of threaded boltsextending through said bolt openings; wherein each said bolt includes aball-shaped end which is received in one of said bolt openings.
 19. Adevice in accordance with claim 18, further comprising a leveling bubblesecured in said upper body member.
 20. A device in accordance with claim18, wherein said body members are composed of tempered aluminum.
 21. Adevice in accordance with claim 18, further comprising a laser beamgenerator between said upper and lower body members for generating avisible light beam; and further including means for directing said lightbeam upwardly and downwardly along a vertical axis through said lightbeam openings in said upper and lower body members.
 22. A device inaccordance with claim 21, wherein said means for directing said lightbeam upwardly and downwardly along said vertical axis comprises a prismwhich intersects said visible light beam from said generator.